Phi (Φ, φ, or ϕ) is the 21st letter of the Greek alphabet.

Phi or PHI may also refer to:

Science and technology

Mathematics

  • Golden ratio (φ)
  • Phi coefficient, a measure of association for two binary variables introduced by Karl Pearson
  • Euler's totient function or phi function
  • Cyclotomic polynomial (<math>\Phi_n(x)</math>)
  • Integrated information theory (IIT) the symbol of which is φ is a mathematical theory of consciousness developed under the lead of the neuroscientist Giulio Tononi
  • Standard normal distribution, <math>\Phi(x)</math> notating its cumulative distribution function and <math>\phi(x)</math> its probability density function

Physics, chemistry and biology

  • Phi meson, in particle physics
  • Magnetic flux (Φ)
  • Peptide PHI (Peptide histidine isoleucine)
  • 6-phospho-3-hexuloisomerase, an enzyme
  • Phenyl group (Φ), a functional group in organic chemistry
  • Pre-harvest interval
  • pH(I), the isoelectric point

Computing

  • Xeon Phi, an Intel MIC microprocessor
  • Φ (Phi) function, in static single-assignment form compiler design
  • Codename for the Nokia Lumia 920
  • Phi (language model)

Medicine

  • Permanent health insurance, against becoming disabled
  • Protected health information, in US law

Other science

  • Phi phenomenon, in visual perception
  • Krumbein phi scale, for the size of a particle or sediment

Arts and entertainment

  • Phi (KinKi Kids album) (2007)
  • Phi (Truckfighters album) (2007)
  • Sailor Phi, a villain in the Sailor Moon manga
  • Phi, a character in the visual novels Zero Escape: Virtue's Last Reward and Zero Escape: Zero Time Dilemma.
  • Phi: A Voyage from the Brain to the Soul, a book by Giulio Tononi (2012)
  • Phi, a character from Beyblade Burst Turbo, a TV show written by Hiro Morita

Organizations

  • Packard Humanities Institute
  • Paraprofessional Healthcare Institute, a nonprofit organization based in New York City, US
  • Pepco Holdings Inc.
  • Petroleum Helicopters International, an American commercial helicopter operator
  • Philadelphia’s major professional sports teams
  • Philadelphia Eagles of the National Football League
  • Philadelphia 76ers of the National Basketball Association
  • Philadelphia Phillies of Major League Baseball
  • Philadelphia Flyers of the National Hockey League
  • Post-Polio Health International
  • Phi, a collegiate secret society at Princeton University

Other uses

  • Voiceless bilabial fricative (IPA symbol: )
  • Phi, a village in Sesant, Cambodia
  • Phi, ghosts in Thai culture
  • Philippines, IOC country code

See also

  • Փ, a letter of the Armenian alphabet
  • PHI-base (Pathogen–Host Interaction database)
  • Kamen Rider 555 or Masked Rider Φ's